The invention relates to gas turbines and, more particularly, to a system and method for measuring turbine bucket creep deformation and determining a time to bucket replacement.
Certain gas turbines experience outward radial deformation due to creep in turbine blades. Turbine blades experience a high temperature environment and operating stresses that can result in tip shroud deflection. Outward radial creep deflection of the bucket tip shroud can lead to bucket tip shroud disengagement resulting in loss of aeromechanical vibration damping and possibly blade liberation.
The current methodology employed to calculate tip shroud radial creep requires unit shutdown and a process involving a borescope inspection. The borescope takes a step reading for all buckets on the wheel (in an exemplary turbine, there are 92 buckets on the stage 2 and stage 3 wheel). A problem with the current methodology is that the inspection requires unit shutdown, which can result in substantial cost and lost power generation.
It would be desirable for a system to calculate bucket life due to radial creep without requiring unit shutdown.